"A comet in the night sky is an awe-inspiring sight.
People throughout history have sometimes seen comets as portents of doom. However, God warned the people of Israel not to fear such signs in the heavens:
Thus says the LORD: Do not learn the way of the Gentiles; do not be dismayed at the signs of heaven, for the Gentiles are dismayed at them. Jeremiah 10:2
Comets are indeed a sign of sorts, but not in the way many ancient people thought.
Because material escapes from the comet nucleus during each 
approach toward the sun, the comet eventually loses all its volatile material. At that point, the comet nucleus can no longer produce a coma or tail, and the comet won’t be visible even though its rocky core may still remain.
A comet nucleus usually has enough volatile material to be continuously expelled for around 10,000 years.
Secular scientists claim that comets are leftover fragments from the formation of the solar system 4.6 billion years ago. If comet nuclei are billions of years old, why are thousands of comets still visible? Creation scientists would argue that this is because both comets and our solar system are only about 6,000 years old.
--Comets’ short lifetimes
--and the absence of a plausible way to replenish them over billions of supposed years
------------testify that our solar system is young, fully consistent with the Bible’s 6,000-year timescale. Comets are a reminder that since God’s Word has told us the truth about Earth’s history and the creation of the universe." ICR